Corrosion inhibiting method and composition



United States Patent C M John F. Lyons, Rolling Hills, Califi, assignor to The Texas Company, New York, N, Y., a corporation of Delaware No Drawing. Application May 28, 1954 Serial No. 433,257

2 Claims. (Cl. 106-14) The present invention relates to a novel corrosion inhibiting composition for coating metal bodies to prevent corrosion, and to a novel method for protecting such metal bodies from corrosion. It is particularly concerned with such a composition and method for preventing the rusting of steel and other ferrous metal bodies.

It is well known that metal bodies, particularly those of ferrous metal, tend to corrode after various fabricating operations have been performed upon them. To reduce corrosion it has been customary to coat such metal bodies with an oily composition between mill operations. An especially difiicult problem has been presented when steel bodies are heated to a high temperature and then quenched in a molten salt bath. When ordinary coating oils are applied to such a steel body after removal from the salt bath, it is found that those sections of the body incrusted with salt still tend to rust excessively because the salt is deliquescent and absorbs moisture from the atmosphere, thus setting up a localized rusting condition which is not alleviated by ordinary oils.

In an effort to solve the problem described above, saltquenched steel bodies were coated with a petrolatum base compound composed essentially of petrolatum, lubricating oil, a light petroleum solvent, and rust inhibiting ingredients. When this compound was mixed with an equal volume of kerosene and applied to salt quenched steel bodies it was found that oxidation was prevented on those metal surfaces which were free from salt, but that severe corrosion still occurred on those areas which were incrusted with deliquescent salt, probably because absorbed moisture could not be displaced.

In accordance with the present invention a novel corrosion inhibiting composition is provided which overcomes the disadvantages discussed above. In its broadest aspects the novel composition is composed predominantly of a soluble oil (say 60-72% by Weight), petrolatum (say 27-39% by weight), and at least one rust inhibiting compound (say up to 3% by weight). The soluble oil is believed to act by displacing moisture from the salt incrusted areas, by forming an emulsion with the moisture thereby making the affected areas wettable with the petrolatum composition, or by a combination of both actions. In any event, corrosion is efiectively prevented in such areas by coating them with my novel corrosion inhibiting composition.

The described composition can be applied to metal surfaces in any suitable way, as by brushing, spraying, or dipping.

A soluble oil is an oil solution that disperses readily when added to water; it is a clear oil solution that is selfernulsifying when combined with water. Soluble oils are prepared by making a solution of the oil and various soaps and emulsifying agents producing clear solutions. When water is mixed with the soluble oil a milky emulsion is readily formed.

The preferred soluble oils are prepared from distillate mineral lubricating oils, particularly naphthem'c oils and oils of low or medium viscosity. The lubricating oil 2,836,499 Patented May 27, 1958 may be compounded with various oil-soluble alkali metal soaps such as rosin soap, or emulsifying materials such as sulfonates, particularly mahogany sulfonates, naphthenates and resinates. Various substances may be included in the soluble oil mixture, such as mutual solvents of the oil and water, emulsifying agents, and viscosity reducing solvents. Higher boiling alcohols improve the emulsifying properites. The soluble oil sloutions are homogeneous or clear solutions and when they are added to water readily form highly stable emulsions.

By way of example, a soluble oil was prepared from the following materials; ranges of composition being specified for the more important ingredients:

The lubricating oil used in the preparation of this soluble oil was a naphthenic base lubricating oil having a viscosity of 76-75 seconds at 109 F. Saybolt Universal (76-75 S. U. S. at R), a gravity of ZZZ-25 API, and a flash point, COC, of 290 F. minimum.

The sodium sulfonate oil mixture was obtained by treating mineral lubricating oil with sulfuric acid and caustic soda and extracting the sodium sulfonates (a form of mahogany sulfonate). The extracted sulfonates were fiuxed with lubricating oil to form the sodium sulfonate oil mixture.

The rosin was dissolved in some of the lubricating oil and sodium sulfonate oil mixture under the application of heat. The naphthenic acid and the caustic solution were added and saponification effected to form sodium naphthenate and rosin soap, after which the water, the ethylene glycol monobutyl ether and the rest of the sodium sulfonate oil mixture and lubricating oil were added.

The petrolatum and one or more corrosion inhibitors can be incorporated with the above-described soluble oil in any suitable way. A petrolatum base compound containing corrosion inhibitors advantageously is made up separately, and then this compound is later combined with the soluble oil.

In one example of how to make up a petrolatum base compound the ingredients listed below are mixed together in the specified proportions while heating mildly as at 100 F., for fluidity. Ranges are specified on the more important ingredients.

The Stoddard solvent is an example of a type "of light volatile petroleum solvent that can be employed to prepare a petrolatum base compound of the desired consistency, others being light and heavy kerosenes or naphviscosity at 210 F. of 95-105 seconds, and a flash point;

COC, of 480 F. minimum.

a The lubricating mineral oil used in the petrolatum base compound may be a naphthene base distillate lubricating oil such as one having a Saybolt Universal viscosity at 100 F. of 200-216 seconds, a gravity of 2023 API, and aflash point, COO, of 330 F. minimum. Another suitable lubricating oil is a steam-refined cylinder stock having a Saybolt Universal viscosity at 210 F. of 155- 163 seconds, a flash point, COC, of 525 F. minimum, and a gravity of 21-24 API. I prefer to use a mixture of these two types of lubricating oil in such'proportions by volume that the petrolatum base compound contains about 8.1% by weight of the former as a softening'agent for the petrolatum, and about 15.6% by weight of the latter to soften the petrolatum and provide a smooth blend. Ranges of -10% and -20%, respectively, are

suitable. r

In the petrolatum, base compound described above, the principal rust inhibitors are the aluminum stearate, butyl stearate, and sodium chromate decahydrate. These should be present in such quantity as to provide in the final composition a corrosion-inhibiting amount up 'to 3% by weight. 7

While one petrolatum base compound has been described in detail above, it is evident that all of the minor constituents described need not necessarily be present to provide the important fundamental advantages of the present invention. It also should be aparent that additional ingredients may be included without substantially altering the corrosion inhibiting properties of the composihibitors may be replaced by one or-two of the same group,

or entirely different corrosion inhibitors may be included in the composition.

After separately preparing the soluble oil and the 4 i a ent invention there is set; forth below the proportions by weight of the added ingredients based on the final diluted rust inhibiting composition, advantageous ranges being specified for the more important ingredients:

Example, Advantage- Weight, ous, Range, Percent Weight, Percent Light Petroleum Solvent 53. 3

Kerosene (47. 4) (5. 9) Petrnl m 12. 7 Lubricating Oil 27. 2

1. 9 1. 1 1.0 7 6 3 3 6 Aluminum Stearate" (.2) Butyl Stearate 3) Sodium Chromate Decahydrate- 1) Sodium Soap of Wool Grease; 01 Balance of incidental ingredients and impurires.

Any amount of the rust inhibitor is helpful, a corrosion inhibiting amount up to 1.5% usually being completely satisfactory (up to about 3% based on the composition without solvent).

In an example of how the corrosion inhibiting composition of the invention was employed, a composition-was ing the parts through other steps in the manufacturing process.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, maybe made with- I out departing from the'spirit and scope thereof, and

I therefore only such limitations should be imposed'as are petrolatum base compound by the procedures described in detail above, the two are combined and mixed to produce the novel composition of the present invention. I have found that superior results are obtained by combining the components in the proportions of one gallon (7.8 lbs.) of soluble oil to 1.1. gallons (8 lbs.) of petrolatum base compound.

After thorough mixing in a suitable container, the resulting mixture is diluted with a light volatile petroleum solvent such as kerosene or Stoddard solvent in an amount equal to the volume of the mixture before dilution. Thus 2.1 gallons (14.3 lbs.) of kerosene can be combined with the mixture described above to produce a final composition which is applied to salt quenched steel bodies for preventing their corrosion after-removal from the salt 4l-45 API, 10% of which distills below 347 F. and 70 95% of which distills below 465 F.

The-ingredients of the composition of the invention have been described in detail above as employed in formulating the individual soluble oil and petrolatum base compounds. For a more complete teaching of the pres-..

indicated in the appended claims.

I.claim:

1. A rust inhibiting coating composition characterized by the ability to prevent rustingof areas on salt quenched steel articles which are encrusted with residual salt, said composition consisting essentially of 44-58% by weight of light volatile petroleum solvent, the balance being a mixture ofa rust inhibiting compound, petrolatum'rand soluble oil, said mixture consisting essentially of a corrosion inhibiting amount'up to 3% by weight of at least one rust inhibiting compound selected frompthe group consisting of butyl stearate, aluminum stearate and sodium chromate decahydrate,: 27-39% by weight of petrolatum and 60-72% by weight of a soluble oil, said'soluble oil having as essential components 60-75% by weight of lubricating oil, 14-18% by weight of sodium sulfonate derived from treating mineral lubricating oil with sulfuric acid'and caustic soda, rosin soap derived from treating with caustic soda 3-5% byweight of gum rosin based on said soluble oil, sodium'naphthenate de-. rived from treating with caustic soda 6-8%' by weight of naphthenic acid based on said soluble oil and .an-efiective amount up to about 1% by weight of ethylene glycol monobutyl ether. 7 I V 2. A method of protecting from rusting an area on a salt quenched steel article which is'encr'usted with residual salt, said method comprising applying tofsaid area a rust-inhibiting coating of a composition consisting essentially of 44-58% by weight of a light volatile pe-- mixture consisting essentially ofa corrosion inhibiting amount up to 3% by weight of at least one rust inhibiting compound selected from the group consisting of butyl stearate, aluminum stearate and sodium chromate decahydrate, 27-39% by weight of petrolatum, and 60- 72% by weight of soluble oil, said soluble oil having as essential components 6075% by weight of lubricating oil, 1418% by weight of sodium sulfonate derived from treating mineral lubricating oil with sulfuric acid and caustic soda, rosin soap derived from treating with caustic soda 35% by weight of gum rosin based on said soluble oil, sodium naphthenate derived from treating with caustic soda 6-8% by weight of naphthenic acid based on said soluble oil and an effective amount up to about 1% by weight of ethylene glycol monobutyl ether.

References Cited in the file of this patent UNITED STATES PATENTS 2,078,256 Lieber et a1. Apr. 27, 1937 2,119,553 MacLaren et a1. June 7, 1938 2,182,992 Lebo Dec. 12, 1939 2,231,214 Nelson Feb. 11, 1941 2,294,717 Carney Sept. 1, 1942 2,307,744 Liberthson Jan. 12, 1943 2,320,263 Carlson May 25, 1943 

1. A RUST INHIBITING COATING COMPOSITION CHARACTERIZED BY THE ABILITY TO PREVENT RUSTING OF AREAS ON SALT QUENCHED STEEL ARTICLES WHICH ARE ENCRUSTED WITH RESIDUAL SALT, SAID COMPOSITION CONSISTING ESSENTIALLY OF 44-58% BY WEIGHT OF LIGHT VOLATILE PETROLEUM SOLVENT, THE BALANCE BEING A MIXTURE OF A RUST INHIBITING COMPOUND, PETROLATUM AND SOLUBLE OIL, SAID MIXTURE CONSISTING ESSENTIALLY OF A CORROSION INHIBITING AMOUNT UP TO 3% BY WEIGHT OF AT LEAST ONE RUST INHIBITING COMPOUND SELECTED FROM THE GROUP CONSISTING OF BUTYL STEARATE, ALUMINUM STEARATE AND SODIUM CHROMATE DECAHYDRATE, 27-39% BY WEIGHT OF PETROLATUM AND 60-72% BY WEIGHT OF A SOLUBLE OIL, SAID SOLUBLE OIL HAVING AS ESSENTIAL COMPONENTS 60-75% BY WEIGHT OF LUBRICATING OIL, 14-18% BY WEIGHT OF SODIUM SULFONATE DERIVED FROM TREATING MINERAL LUBRICATING OIL WITH SULFURIC ACID AND CAUSTIC SODA, ROSIN SOAP DERIVED FROM TREATING WITH CAUSTIC SODA 3-5% BY WEIGHT OF GUM ROSIN BASED ON SAID SOLUBLE OIL, SODIUM NAPHTHENATE DERIVED FROM TREATING WITH CAUSTIC SODA 6-8% BY WEIGHT OF NAPHTHENIC ACID BASED ON SAID SOLUBLE OIL AND AN EFFECTIVE AMOUNT UP TO ABOUT 1% BY WEIGHT OF ETHYLENE GLYCOL MONOBUTYL ETHER. 